Bring to mind your last straight-out-of-the-box experience with a disposable medical device of any kind. Without a doubt, everyone has experienced the same frustrations: ambiguous instructions printed too small to read easily, and difficult assemblies that simply don't match up with human capabilities. As an industry and a profession, medical product developers have vast knowledge on how human beings perceive and process information and on how human hands work. Surprisingly, not much of that knowledge manages to inform the design of medical disposables, test kits, and instructions for use (IFUs). With an eye toward higher functionality and usability in disposables, test kits, and IFUs, this article reviews fundamental factors critical to successful design plus common oversights that lead to design disasters.

Fingers can sense a raised dot 3 μm high. For perspective, hair ranges from 80 to 120 μm. (Credit: Metaphase Design Group)

Using the Product

For design purposes, anyone who touches a product is a “user.” That very broad population for disposables, test kits, and IFUs includes patients, family members, home health workers, and healthcare professionals — who come in different sizes and shapes, with varying degrees of functional and cognitive capabilities. Successful design works to accommodate the broad range of user physicality and prowess. The good news is that even across the diversity of humans, all hands share common functionality and sensibility that can be accommodated by good design.

On a smooth surface, fingertips gauge sensory impact as small as a 3 μm texture. Everyone has a smart, dominant hand, and the other, “dim-witted” hand. Smart hands routinely use thumb, index, and middle fingers to execute high-precision and dexterous acts. Ring and pinky fingers work in parallel to grasp and secure objects. Consider the familiar one-handed bottle opening move: the user's ring and pinky fingers grasp the bottle and the middle, index and thumb fingers adroitly unscrew the cap.

Good design in disposables comes from the comprehensive understanding of how hands work and using that knowledge to create optimum functionality. User gender and age are key to successful design. A small female hand and a large male hand can vary as much as 1.75 in. in length and 1.25 in. in width, vast differences that significantly impact usability in a handheld disposable device. Long fingernails that extend beyond the tip of the finger dramatically reduce dexterity and tactile feedback. The reduction in finger strength between a 25-year-old and a 65-year-old female can be more than 50 percent, a difference that can render a product ferociously difficult to use for significant numbers of intended patients.

These fundamental human factors directly impact the ability of everyday people to use lifesaving auto injectors such as delivering NARCAN® for opiate overdoses and EpiPen® to administer epinephrine for anaphylaxis. Design that accommodates a grandmother, who has a fractional amount of standard hand dexterity, range of joint motion, and finger strength as she tries to grasp, position, and actuate these types of auto injectors can mean the difference between life and death.

Fifth percentile female hand in comparison to 95th percentile male hand.(Credit: Metaphase Design Group)

Shape, form, pressure, force, rotary, or pull motions — all are common ergonomic and design factors to consider for successful disposable devices. Consider:

  • Diabetics deal with neuropathy in fingertips and vision issues.

  • Rheumatoid arthritis patients have between 5 and 10 percent less fingertip strength and dexterity than a healthy hand.

  • Multiple sclerosis patients frequently deal with tremors and motion control of the arm and hand.

  • Osteoarthritis affects one-fifth of the adult U.S. population, resulting in range of motion and strength issues.

In the realm of unintended consequences, there are market pressures that affect the usability of disposable products. In general, profit in disposable products comes from volume, which encourages the use of the inexpensive materials, using the least amount of material as possible — which is a key cost factor — and opting for the most efficient manufacturing process. That's designing for manufacturing processes, not for patients, and it results in disposable mechanisms that don't work well that have poor usability qualities — buttons that are too small, forces that exceed an aged or unhealthy hand, and compromised visual feedback. To achieve better, higher-performing products, disposable device manufacturers must build-in both usability and profitability in their design briefs. It is important to note that good design does not mean expensive design solutions. Good design means thinking differently and driving decisions from a user's perspective while respecting cost, materials, and manufacturing processes.

As with durable medical devices, FDA mandates usability standards for all disposable products. Concepts and designs must be tested with all types of users in sufficient numbers to guarantee reliability, ensure that all potential use errors are designed out, and warrant that functional usability is optimized. But it is not just the design of the disposable products users touch that interests FDA. Of equal interest and possibly of greater impact on success are the product IFUs.

Following the Directions

A disposable device or test kit can deliver all the technology, chemistry, and medical science in the world to the patient's doorstep, but it's all worthless if the patient can't figure out how to use it. Poor patient instruction causes confusion which, in turn, increases stress for users who are both uncertain whether the drug or test will be administered properly and what the impact will be on their health.

There is an inverse correlation between the amount of instruction and the efficacy of the product design. Bad designs need excessive instruction to overcome their inadequacies. Good design cues the user through affordances that shape and guide user behavior for the optimal use outcome. The foundation of effective IFUs is clear and concise language accompanied by unambiguous visual cues to mitigate use error.

First and foremost, it is important to structure the IFU so that users do not get lost in a series of ongoing steps. People process information, or in human factors terms, create digestible information in “chunks.” After seven chunks of information, there is a significant falloff in memory. Research shows that IFU or Quick Start Guide content is most effective when presented to users in three to five steps. This fundamental IFU design guideline signals simplicity and accessibility to the user and provides a straightforward instruction architecture that empowers users to quickly and easily comprehend its meaning.

Example of IFU ergonomic and design audit in search of simplicity and intuitiveness.

There's a long-standing, vigorous debate on the efficacy of illustrations versus photos to support instructional materials. As a rule of thumb, use illustrations to emphasize more efficiently the exact action and to focus the user on a specific step, eliminating all extraneous visual noise that commonly occurs in photographs. A video IFU is the current big idea but is not as accessible as it might seem. Consider that aging and poorer populations often those with the highest prevalence of chronic diseases treated by disposable devices or tested through an at-home kit, have lower rates of Internet use and access than the broader population. Thorough knowledge of the user drives the content and the communications medium of successful IFUs.

It's important to understand the differences between on-product guidance and instructional materials. Successful on-product labels that guide usability rely on simply illustrated and intuitive high-contrast figures and icons using no more than three steps. Those three steps, in turn, are unpacked in the full instructional materials, but they never violate the caveat of the five steps maximum in any segment of instructional information.

Test kits bring a unique design challenge to IFUs when the user reads the results. Ensuring that the user is interpreting the results correctly and engaging in the correct behavior predicated on those results puts a heavier burden on design for user instruction. Common human factors to consider are colorblindness, visual acuity, and cognitive ability. Test kits that require time-based decisions and actions further complicate usability, especially for elderly users. These human factors all have the potential to dramatically affect the interpretation of results and the required or recommended actions the patient must take in response to the test results.

Regarding IFUs, FDA states that usability testing applies as stringently to instructions as it does to disposables and devices. There are two types of testing in the FDA process: formative and summative. Formative testing occurs in multiple iterations at all stages of the IFU development and rolls up into the summative testing and report filed with FDA. Below are a few best practices for IFU formative and summative tests:

  • Small batch testing with quick turns — test 5–10 people, then tweak the IFU; test another 5–10 people, then tweak.

  • Multiple formative tests, especially for instructions — “one and done” will not get the results needed.

  • Aim for two to six formative study types per project, with multiple subtests in each type (applies to IFUs as well as disposables or test kits).

  • The design must accommodate parallel formative testing on everything inside the test kit, the test kit packaging, and all labeling.

  • Keep in mind that all formative testing will roll up into a highly focused, comprehensive formative study that sets the stage for a successful summative study for the FDA filing.

Design with Dignity and Human Factors

There is a direct connection between human dignity and patient compliance. To get the latter, design in the former.

Complicated IFUs and disposable designs and test kits that are difficult to use, unintuitive, and confusing transmit a powerful, yet negative value message to the user. Unless the patient has bulletproof self-confidence, the user gets a dose of negative self-image that erodes dignity and directly decreases compliance. Beyond issues of compliance, a design succeeds when it enables a positive use of the product and empowers a positive state of mind in the user.

A real-world example of nightmare design is a test kit that looks like an advanced biochemistry set, with an IFU that unfolds to six square feet of eight-point type and 70 steps to complete the test. Keep in mind that a test kit user is almost always a person who is ill, or nervous, about finding out that he or she is ill. Good design respects the patient.

Dignity is not an option. It is a human right of every patient, and it must be addressed in the design of all disposables, test kits, and IFUs. The bonus is that building in respect and dignity for the user prompts a dramatic uptick in the patient's frame of mind, compliance, and overall mental fitness to use the product, which, in turn, encourages more product sales.

Making disposables that are usable means making them human-friendly. Front-loading design into the product development process for disposables and test kits, and applying human factor guidance to IFU testing, will produce products that will pass usability requirements with flying colors, and importantly, empower patients for successful selfcare and drive shareholder value.

This article was written by Dr. Bryce Rutter, founder and CEO of Metaphase Design Group Inc., St. Louis, MO. To view Metaphase's portfolio of medical instruments, devices, surgical systems, drug delivery, and disposables, visit here. For more information, visit here.